Single-pole switch power source

ABSTRACT

A single-stage switched-mode power supply comprises: a dual-source ac rectifying unit ( 501 ), for converting an alternating current input by an alternating current power source into at least two direct current sources, namely, a first direct current source ( 606 ) and a second direct current source ( 607 ); a combination switch unit, at least comprising a first switch circuit ( 603 ) and a second switch circuit ( 605 ), used for respectively performing power conversion on the first direct current source ( 606 ) and the second direct current source ( 607 ), to output a direct current, wherein the first direct current source ( 606 ) is connected to the first switch circuit ( 603 ) through an energy-storage capacitor ( 604 ), the first switch circuit ( 603 ) is any circuit capable of functioning as a switch circuit, and the second switch circuit ( 605 ) is a circuit capable of functioning as a flyback switch circuit. The single-stage switch power supply has complete power factor correction and output hold-up time, and further improves power source conversion efficiency.

This application is the U.S. National Stage of International ApplicationNo. PCT/CN2012/087128, filed Dec. 21, 2012, which designates the U.S.,published in Chinese. The entire teachings of the above application areincorporated herein by reference.

TECHNOLOGY AREA

The present disclosure provides a single-stage switched-mode powersupply (SMPS).

BACKGROUND

Electricity is among the most convenient and widely used energy form.With the ever increasing rate of energy use, there is increasingattention on energy efficiency, especially on increasing the powerconversion efficiency of the SMPS. As it is often the input power supplyof many appliances, the SMPS contributes a large part to the appliance'soverall efficiency, which can only be lower than that of the SMPS.

FIG. 1 through 4 are schematic depictions of four prior artsingle-transistor, single-stage high-frequency SMPS topologies. Theirimplementations are limited to low-power ac-dc power conversion. Thesimplest topology of FIG. 1 contains an active clamp network 101. It hassignificant drawbacks when used in low-voltage high-current outputapplications, due to the need of large output capacitance for energystorage, the complexity of clamp network control and associated minimalamount of loss. The drawbacks in topology of FIG. 2 are present in addedsize and cost of the two rectifier diodes and their contribution to theclamp network's losses. The drawbacks in topology of FIG. 3 are presentas results of the additional half conversion stage, the controlcomplexity of achieving unity power factor and the large current stressand related loss in the power switch during turn-on resulting fromstored energies in the inductor and transformer. The topology in FIG. 4suffers from issues such as low efficiency, the addition of tworectifiers which increases converter loss, size and cost, and similarproblems associated with the power switch as described for the FIG. 3topology.

To meet the many high-end power management requirements, a modern SMPSneeds to be highly efficient and contains advanced technologies such asinterleaving, soft-switching, synchronous rectification, outputmanagement and reduced power conversion stages. In contrast, theperformance of single-stage SMPS with prior art technologies has notseen a dramatic increase, making their commercialization difficult.

SUMMARY

The present disclosure provides a single-stage SMPS. The SMPS comprisesof, a dual-source ac rectifying unit, used to convert an input ac sourceand generate at least two new (first and second) dc sources; a combinedswitching cell, comprised of first and second switching circuits usedfor power conversion from the first and second dc sources, with the twocircuits' outputs paralleled and producing dc; connection of the firstdc source and switching circuit via a bulk capacitor; the firstswitching circuit being any switched-mode topology; the second switchingcircuit being the flyback-derived topology.

By using a topology with dual-source single-stage, active clamping,multi-phase interleaved switching and integrated control properties, thepresent disclosure can realize improved power conversion efficiencywhile retaining complete control of ac power factor correction and powersupply output hold-up time.

To allow for easy understanding of the present disclosure's features andmerits, the remaining text provides detailed description along withdrawings and embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

To better clarify embodiments of and technologies used in prior art andpresent disclosure, the following descriptions of their drawings areprovided. The embodiments contained herein should not be limited todisclose embodiments but rather should be limited only by the spirit andscope of the appended claims. It will become apparent to one of ordinaryskill in the art that other embodiments incorporating the same conceptsmay also be used.

FIG. 1 is a schematic depiction of a prior art SMPS topology;

FIG. 2 is a schematic depiction of a prior art SMPS topology;

FIG. 3 is a schematic depiction of a prior art SMPS topology;

FIG. 4 is a schematic depiction of a prior art SMPS topology;

FIG. 5 is a system block diagram of the single-stage SMPS in thedisclosure;

FIG. 6 is a schematic depiction of topology used in the single-stageSMPS in the disclosure;

FIG. 7 is a waveform diagram of currents and voltages in thesingle-stage SMPS in the disclosure;

FIG. 8 is a schematic depiction of topology used in the single-stageSMPS in the disclosure;

FIG. 9 is a schematic depiction of topology used in the single-stageSMPS in the disclosure;

FIG. 10 is a schematic depiction of topology used in the single-stageSMPS in the disclosure;

FIG. 11 is a schematic representation of a single-stage SMPS inaccordance with exemplary embodiments of the disclosure;

FIG. 12 is an integrated circuit diagram of controller used in asingle-phase single-stage SMPS in accordance with exemplary embodimentsof the disclosure;

FIG. 13 is another schematic representation of a single-stage SMPS inaccordance with exemplary embodiments of the disclosure;

FIG. 14 is another integrated circuit diagram of controller used in adual-phase single-stage SMPS in accordance with exemplary embodiments ofthe disclosure;

DETAILED DESCRIPTION

The embodiments of the present disclosure are now described in fulldetail using their drawings previously given. The embodiments containedherein should not be limited to the disclosed embodiments but rathershould be limited only by the spirit and scope of the appended claims.Other embodiments incorporating the same concepts may be developed byone of ordinary skill in the art and shall be protected by the presentdisclosure.

This disclosure provides a single-stage SMPS. FIG. 5 shows the systemblock diagram of the single-stage SMPS in the disclosure. It includes adual-source ac rectifying unit 501, used to convert an input ac sourceand generate at least two new sources (first and second) with dc orquasi-dc characteristics, a combined switching cell 502, comprised offirst 5021 and second 5022 switching circuits, is used for powerconversion from the first and second dc sources, with the two circuits'outputs paralleled and producing dc. The first dc source and switchingcircuit are connected via a bulk capacitor. The second switching circuitis of the flyback-derived topology. The dual-source ac rectifying unitincludes two rectifier bridges, where the bridges' input ac terminalsare paralleled, and the bridges' negative dc output terminals are tiedtogether. Together, they convert input ac to two dc sources.

The single-stage SMPS of the disclosure also provides a current mergingunit 503 and a dual-source controller unit 504. The current merging unitis used to deliver the charging current from the combined switching cellback to the ac source, and forms a closed loop. The dual-sourcecontroller unit is used to control the first and second switchingcircuits in the combined switching cell 502.

FIG. 6 shows a schematic depiction of topology used in the single-stageSMPS in the disclosure. A dual-source ac rectifying network is formedusing rectifier bridges 601 and 602, with their ac input terminalsparalleled and negative dc output terminals tied. This network containstwo ac input and three dc output terminals and converts single-phase acinto two dc sources. Dc source 606 contains a large capacitor 604, usedas an energy-storage source. Dc source 607 contains no capacitor and isa time-varying voltage source. This combination of two dc sources formsa dual-source dc supply. The dc output of the SMPS is generated fromconverter cells 603 and 605. Converter 605 is connected to dc source 607and is of the flyback-derived topology. Converter 603 is connected to dcsource 606 and energy-storage capacitor 604. In addition, converter 603can be realized with any switched-mode circuit topology, including butnot limited to forward, flyback, push-pull and half or full-bridge. Thetwo converters' dc outputs are parallel-connected and store energy inoutput capacitor 609.

The single-stage SMPS of the disclosure also contains a line-frequencycurrent merging network, which consists of two series-connectedcurrent-sensing resistors. The first end terminal of the resistornetwork is connected to the ac rectifying unit's negative output. Thesecond end terminal is used to sink the line-frequency time-varyingcurrent I_(PFC), which is current flowing through converter 605 and isused by the SMPS to control the ac current. The middle terminal is usedto sink the line-frequency charging current I_(CHG), which is thecurrent flowing through converter 603 and describes the charging currentin capacitor 604 due to ac. The total current flowing through the SMPSis I_(AC), and the relationship between the three currents is asfollows: I_(AC)=I_(CHG)+I_(PFC).

Waveforms in FIG. 7 show graphically this relationship. The voltage onthe energy storage is V_(CHG) and is essentially constant dc with smallripple. The voltage from the time-varying source is V_(AC) and has afull-wave rectified waveform following that of input ac. The magnitudeand waveform of charging current I_(chg) is only dependent on the SMPSoutput load. The total SMPS input current I_(AC) is dependent on bothload and ac power factor. The time-varying current I_(PFC) is uniquelydetermined by the above two currents and expressed as follows:I_(PFC)=I_(AC)−I_(CHG).

The time-varying current I_(PFC) becomes one of the controlled variablesof the dual-source controller. This quantity is used to achieve ac powerfactor correction.

The dual-source ac rectifying unit can be realized with at least fourdifferent circuit topologies, as shown in FIGS. 6, 8, 9 and 10. FIG. 6shows a dual-source ac rectifying unit realized with eight dioderectifiers. FIG. 8 shows a dual-source ac rectifying unit realized withfive diode rectifiers. FIG. 9 shows a dual-source ac rectifying unitrealized with two diode rectifiers. FIG. 10 shows a dual-source acrectifying unit realized with six diode rectifiers.

During the operation of the flyback converter cell used in thisdisclosure, the transient energy change developed by the transformerprimary winding needs to be suppressed by a clamping circuit. Theclamping circuits used in embodiments of this disclosure are classifiedas primary-side and secondary-side lossless voltage-clamp networks. Theyare used to suppress voltage transients that occur during the switchturn-off period in the second switching circuit. The secondary-sidelossless voltage-clamp network includes a series-connected inductor andcapacitor network, in which the first inductor terminal is connected tothe transformer's secondary-side output in the second switching circuit,and the second inductor terminal is tied with the first capacitorterminal, and the second capacitor terminal is connected to thetransformer's secondary-side ground. The primary-side losslessvoltage-clamp network includes a series-connected inductor and capacitornetwork, in which the inductor is made up of a section of thetransformer primary winding in the second switching circuit, and thefirst inductor terminal is connected to the switching device's drain orcollector terminal, and the second inductor terminal is tied with thefirst capacitor terminal, and the second capacitor terminal is connectedto the transformer primary winding's input ground. Further detaileddescription of the embodiments of this disclosure is now provided usingtwo application examples.

Application Example #1

FIG. 11 shows a schematic of a dual-source single-phase single-stageac-dc SMPS. It consists of ac rectifying bridges 1101 and 1102, largeenergy-storage capacitor 1103, transformers 1104 a and 1104 b,primary-side lossless voltage-clamp network 1106, power switch 1108,diode rectifier 1109 and single-phase single-stage SMPS dual-sourcecontroller integrated circuit (IC). Through rectifying bridges 1101 and1102, the ac input is decomposed into two dc sources, which are referredto as energy-storage source 1111 and time-varying source 1112. These twosources together form a dual-dc source. They differ in that theenergy-storage source contains a large energy-storage capacitor 1103,which is not present in the time-varying source. The energy-storage andtime-varying sources are connected to primary windings of transformers1104 a and 1104 b respectively, the other ends of which are connectedpower switches 1108 and 1109 respectively. The above components andtheir connections form two single-switch converter circuits. Thetime-varying source is connected to a flyback converter or its variants,such as an interleaved flyback, any other flyback-derived converters ora parallel-connected combination of the above. The flyback converter isused to achieve ac power factor correction and to process on averagehalf the total SMPS power. The energy-storage source is connected to anisolated dc-dc converter of any topology, including but not limited toforward, flyback, push-pull, half/full-bridge or a parallel-connectedcombination of the above. This application chooses the flyback converterto improve the SMPS output characteristics, especially under low voltageand high current conditions. It is also used to maintain hold-up timeand to process on average half the total SMPS power. To suppress thevoltage transient appearing across the power switch, this applicationuses the secondary-side lossless voltage-clamp network 1107.

The dc output voltage 1113 is fed back to the primary-side compositesignal network 1151 through opto-coupler and the output sensing network1114. This voltage feedback signal is combined with the zero-currentdetection signal 1115 to form a synchronizing composite signal SYN,which is connected to controller 1120. The controller's decouplingcircuit then recovers both the zero-current detection signal 1115 andfeedback signal from the output voltage 1113. This single-phasesingle-stage SMPS dual-source controller IC saves one input signal byusing the composite signal to control both converters.

The charging current I_(CHG) in first switching circuit andenergy-storage source 1111 flows through the current-sensing resistor1116. The power factor correction current I_(PFC) in second switchingcircuit and time-varying source 1112 flows through the current-sensingresistor 1117. These two currents flows into ac after merging. The accurrent signal is indirectly sampled by sampling the time-varyingvoltage signal VAC. The power factor correction current signal CS is thesum of voltages on resistors 1116 and 1117 in the current mergingnetwork 1150. This implementation realizes the current relationshipI_(PFC)=I_(AC)−I_(CHG) and achieves power factor correction.

The detailed description of the primary-side lossless voltage-clampnetwork 1106 in this disclosure is now given. The primary-side losslessvoltage-clamp network 1106 includes a series-connected inductor andcapacitor network, in which the inductor is made up of a section of thetransformer 1104 b primary winding in the second switching circuit, andthe first inductor terminal is connected to the drain or collectorterminal of the switching device 1108, and the second inductor terminalis tied with the first capacitor terminal, and the second capacitorterminal is connected to the transformer 1104 b primary winding's inputground. When switching device 1108 turns on, its current consists ofboth the transformer 1104 b primary winding current and the dischargecurrent of the capacitor in clamp network 1106. The energy stored in theclamping capacitor is released and stored in the primary windinginductance. When switching device 1108 turning off, the energy intransformer 1104 b primary winding due to instantaneous change inelectric potential is stored in the clamping capacitor through theclamping inductor. This energy transfer process suppresses losslesslythe energy due to instantaneous change in electric potential. As theclamping inductor is realized with a winding sharing the same magneticcore with the primary winding but with different polarity, the inducedvoltage in the inductor winding further suppresses energy in thistransient.

The detailed description of the secondary-side lossless voltage-clampnetwork 1107 in this disclosure is now given. When power switch 1109 isturned on, the transformer 1104 a primary winding is storing energy, andno current flows in the secondary winding. At same time, the energystored in the capacitor in clamp network 1107 is released to theinductor. The capacitive energy is losslessly transformed into currentin the inductor. The capacitor and inductor energies are togethertransferred to the output load. When power switch 1109 is turned off,the energy in transformer 1104 a primary winding due to instantaneouschange in electric potential is transferred to the capacitor in clampnetwork 1107 through the secondary winding. This energy is quicklyabsorbed and stored in the capacitor. This energy transfer processlosslessly suppresses the energy due to instantaneous change in electricpotential on power switch 1109.

In this application, the voltage transient on power switch 1108 duringturn-off is suppressed by primary-side lossless voltage-clamp network1106. The network 1106 is consisted of a capacitor and inductor. Theinductor winding shares same magnetic core with transformer 1104 b. Thecapacitor is used to clamp the rapidly rising voltage. The inductor isused to recycle energy stored in the capacitor and stores it in thetransformer during its energy-storing period. The clamping performancecan be adjusted via capacitance selection.

In this application, the voltage transient on power switch 1109 duringturn-off is suppressed by secondary-side lossless voltage-clamp network1107. The network's capacitor is used to clamp the rapidly risingvoltage coupled from primary of transformer 1104 a to secondary. Thenetwork's inductor is used to transfer energy stored in the capacitor tooutput capacitor 1110 during the non-output period of the transformer.The clamping performance can be adjusted via capacitance selection. Inboth clamp networks, no dissipative elements participate in the energystorage and recovery processes. Therefore, both are lossless clampnetworks.

FIG. 12 shows integrated circuit 1120 of the single-phase single-stagedual-source controller unit. It contains at least one flyback SMPScontroller 1122, such as the commonly-used L6562 or similar controller.It also contains a flyback SMPS controller 1123, such as thecommonly-used UC3842 or similar controller. It finally contains afeedback signal de-coupler 1124. Controller 1122 is used to controlpower switch 1108. Controller 1123 is used to control power switch 1109.Feedback signal de-coupler 1124 is used to restore the feedbackcomposite signal SYN into zero-current detection signal ZCD and outputvoltage feedback signal FB.

Application Example #2

Shown in FIG. 13 schematic, an interleaved single-stage ac-dc SMPSconsists of at least dual-source ac rectifying bridges 1301 and 1302,large energy-storage capacitor 1303, an interleaved flybackswitched-mode circuit 1304, a circuit 1305 of any switched-mode circuittopology, an optional circuit 1306 also of any switched-mode circuittopology used as standby supply and an interleaved single-stage SMPSdual-source controller IC. FIG. 14 shows schematic drawing of theinterleaved single-stage SMPS dual-source controller IC. Throughrectifying bridges 1301 and 1302, the ac input is decomposed into anenergy-storage source and a time-varying source. These two sourcestogether form a dual-dc source. They differ in that the energy-storagesource contains a large energy-storage capacitor 1303, which is notpresent in the time-varying source. The time-varying source is connectedto a switched-mode circuit based on the flyback topology, therebyenabling power factor correction of the SMPS and processing roughly halfthe total SMPS power. The switched-mode circuit connected to theenergy-storage source can be of any topology, including but not limitedto forward, flyback, push-pull and half/full-bridge. A LLC bridge-typecircuit is used in this application to improve the SMPS outputcharacteristics, especially under low voltage and high currentconditions. It is also used to maintain hold-up time and to process onaverage half the total SMPS power.

The dc output voltage VDC is fed back to the primary-side compositesignal network 1351 through an opto-coupler and the output sensingnetwork 1314. This voltage feedback signal is combined with thezero-current detection signal 1351 to form a synchronizing compositesignal SYN1, which is connected to controller 1320 as shown in FIG. 14.The controller's decoupling circuit 1324 a then recovers both thezero-current detection signal and feedback signal from the dc outputvoltage, thereby saving one input signal.

Standby dc output voltage VSB is fed back to the primary-side compositesignal network 1352 through an opto-coupler and the output sensingnetwork 1344. This voltage feedback signal is combined with thezero-current detection signal to form a synchronizing composite signalSYN2, which is connected to controller. The controller's decouplingcircuit 1324 c then recovers both the zero-current detection signal andfeedback signal from the standby dc output voltage, thereby saving anadditional input signal.

The standby supply in this application uses the flyback topology. Itcontains a synchronizing composite signal network 1353 that consists oftwo resistors. The network's switch current sensing signal CS andzero-current detection signal ZCsb are combined to form a compositesignal Csb. The controller's decoupling circuit 1324 b recovers theoriginal signals CS and ZCsb from Csb, thereby saving another inputsignal.

The charging current I_(CHG) in switched-mode circuit associated withenergy-storage source 1311 flows through current sensing resistor 1316.The power factor correction current I_(PFC) in switched-mode circuitassociated with the time-varying source is the sum of currents I_(PFC)_(_) _(A) and I_(PFC) _(_) _(B), flowing through current sensingresistors 1317 a and 1317 b respectively. These three currents aremerged, and the combined current is delivered to the ac source. The accurrent is indirectly sensed through sensing signal VAC of thetime-varying voltage. The power factor correction currents CSIa and CSIbare sensed through summing the voltages of resistors 1316, 1317 a and1317 b in the current merging network. This results in the followingexpressions for the interleaved power factor correction current:I _(PFC) =I _(PFC) _(_) _(A) +I _(PFC) _(_) _(B);I _(PFC) =I _(AC) −I _(CHG).

This achieves desirable correction of the power factor.

The single-phase single-stage SMPS dual-source controller IC 1320 isconsisted of at least one interleaved flyback SMPS controller 1322 (e.g.commonly-used FAN9612 or similar controller), one LLC resonant SMPScontroller 1323 (e.g. commonly-used UCC25600 or similar controller) andthree signal de-couplers 1324 a, 1324 b and 1324 c. Controllers 1322 and1323 are used to control switched-mode circuits 1304 and 1305,respectively. Feedback signal de-coupler 1324 a is used to recover thefeedback composite signal SYN1 into zero-current detection signal ZCD1and output voltage feedback signal FB. Feedback signal de-coupler 1324 cis used to recover the feedback composite signal SYN2 into zero-currentdetection signal ZCD2 and standby voltage feedback signal FBsb.Synchronizing signal de-coupler 1324 b is used to recover thesynchronizing composite signal Csb into zero-current detection signalZCsb and standby current sensing signal CS.

The dual-source switched-mode circuit in the present disclosure isequivalent to the combination of two conventional switched-modecircuits. Some of the control signals in the two circuits are related.Therefore, complexity reduction and practicality improvements areexpected in the dual-source switched-mode circuit by integratingcontrollers 1122 and 1123 of conventional circuits into single-phasedual-source controller 1120. The same can be achieved by integratingcontrollers 1322 and 1323 of conventional circuits into dual-phaseinterleaved dual-source controller 1320.

The application examples have applied operating principles and explainedimplementations of the present disclosure. The examples' descriptionsonly serve to help one understand methods and fundamental ideas of thepresent disclosure. It will become apparent to one of ordinary skill inthe art that other embodiments incorporating the same concepts may alsobe used. Therefore, the embodiments contained herein should not belimited to be disclosed embodiments.

What is claimed is:
 1. A single-stage switched-mode power supply (SMPS)comprising: a dual-source ac rectifying unit, used to convert an inputac source and generate at least two new sources with dc or quasi-dccharacteristics, the at least two new sources including first and seconddc sources; a combined switching cell, comprised of first and secondswitching circuits used for power conversion from the first and seconddc sources, with outputs from the first and second switching circuitsparalleled after rectified and producing dc output, wherein the first dcsource and the first switching circuit are connected via a bulkcapacitor, with a combined line-frequency charging current, referred toas I_(CHG), flowing through the first switching circuit, and the firstswitching circuit can be of any switched-mode topology wherein thesecond switching circuit is of a flyback-derived topology, with aline-frequency charging current flowing through the second switchingcircuit referred to as I_(PFC), a total input current of the first andsecond switching circuits is referred to as I_(AC), whereinI_(AC)=I_(CHG)+I_(PFC); and a current merging unit, used to merge thecombined line-frequency charging current from the first switchingcircuit with an input current from the second switching circuit toproduce a combined current into the combined switching cell and deliverthe combined current back to the input ac source and wherein: thecurrent merging unit includes at least a series-connected doubleresistor network; a first end terminal of the series-connected doubleresistor network is connected to a negative output of the dual-source acrectifying unit; a second end terminal of the series-connected doubleresistor network is connected to a ground terminal of a switching devicein the second switching circuit and is used to sink a power factorcorrection (PFC) current; a middle terminal of the series-connecteddouble resistor network is connected to a negative terminal of the bulkcapacitor and is used to receive the combined line-frequency chargingcurrent in the first switching circuit and the PFC and the combinedline-frequency charging current are combined and become a merged currentof the combined switching cell, which is delivered to the input acsource.
 2. The power supply according to claim 1, wherein: thedual-source ac rectifying unit includes two rectifier bridges; input acterminals of the two rectifier bridges are paralleled; negative dcoutput terminals of the two rectifier bridges are tied together; andpositive dc output terminals of the two rectifier bridges serve as twooutputs of the dual-source ac rectifying unit.
 3. The power supplyaccording to claim 1, wherein: the combined switching cell includesprimary-side and secondary-side lossless voltage-clamp networks; and theprimary-side and secondary-side lossless voltage-clamp networks are usedto suppress voltage transients that occur during a switch turn-offperiod in the second switching circuit.
 4. The power supply according toclaim 3, wherein: the secondary-side lossless voltage-clamp networkincludes a series-connected inductor and a parallel-connected capacitor;and a secondary-side output winding of a transformer is tied to both afirst terminal of the series-connected inductor and a first terminal ofthe parallel-connected capacitor while a second terminal of theseries-connected inductor is tied to an output terminal of the SMPS anda second terminal of the parallel-connected capacitor is tied to anoutput ground of the SMPS.
 5. The power supply according to claim 3,wherein: the primary-side lossless voltage-clamp network includes aseries-connected inductor and a series-connected capacitor; theseries-connected inductor is made up of a section of a primary windingof a transformer in the second switching circuit; a first terminal ofthe series-connected inductor is tied to a switching device's drain orcollector terminal; a second terminal of the series-connected inductoris tied with a first terminal of the series-connected capacitor; and asecond terminal of the series-connected capacitor is connected to aprimary winding's input ground of the transformer.
 6. The power supplyaccording to claim 1, wherein the single-stage SMPS also includes adual-source controller unit, used to control the first and secondswitching circuits in the combined switching cell.
 7. The power supplyaccording to claim 6, wherein the dual-source controller unit is asingle-phase dual-source control circuit and includes: a flyback SMPScontroller, used to control the second switching circuit; and a dc-dcSMPS controller, used to control the first switching circuit.
 8. Thepower supply according to claim 7, wherein the single-phase dual-sourcecontrol circuit also includes a feedback signal de-coupler, used torestore a combined feedback signal into zero-current detection andoutput voltage feedback signals.
 9. The power supply according to claim6, wherein the dual-source controller unit is an interleaved dual-sourcecontrol circuit and includes: an interleaved flyback SMPS controller,used to control the second switching circuit; and a dc-dc SMPScontroller, used to control the first switching circuit.
 10. The powersupply according to claim 9, wherein the interleaved dual-source controlcircuit also includes a feedback signal de-coupler, used to restore acombined feedback signal into zero-current detection and output voltagefeedback signals.
 11. The power supply according to claim 9, wherein theinterleaved dual-source control circuit also includes a synchronizationsignal de-coupler, used to restore a combined synchronization signalinto zero-current detection and stand-by switching current samplingsignals.
 12. The power supply according to claim 1, wherein: thecombined switching cell includes a primary-side lossless voltage-clampnetwork; and the primary-side lossless voltage-clamp network is used tosuppress voltage transients that occur during a switch turn-off periodin the second switching circuit.
 13. The power supply according to claim12, wherein: the primary-side lossless voltage-clamp network includes aseries-connected inductor and a series-connected capacitor; theseries-connected inductor is made up of a section of a primary windingof a transformer in the second switching circuit; a first terminal ofthe series-connected inductor is tied to a switching device's drain orcollector terminal; a second terminal of the series-connected inductoris tied with a first terminal of the series-connected capacitor; and asecond terminal of the series-connected capacitor is connected to aninput ground of a primary winding of the transformer.
 14. The powersupply according to claim 1, wherein: the combined switching cellincludes a secondary-side lossless voltage-clamp network; and thesecondary-side lossless voltage-clamp network is used to suppressvoltage transients that occur during a switch turn-off period in thesecond switching circuit.
 15. The power supply according to claim 14,wherein: the secondary-side lossless voltage-clamp network includes aseries-connected inductor and a parallel-connected capacitor; asecondary-side output winding of a transformer is tied to both a firstterminal of the series-connected inductor and a first terminal of theparallel-connected capacitor while a second terminal of theseries-connected inductor is tied to an output terminal of the SMPS anda second terminal of the parallel-connected capacitor is tied to anoutput ground of the SMPS.